The present invention relates to a thermal interface material and package thermal design for a semiconductor device which includes a stress-relieving buffer layer.
A flip chip package, more specifically an organic flip chip package, including a flip chip on a multi-layer carrier, inherently warps within a predetermined temperature range because of the coefficient of thermal expansion (CTE) mismatch between the flip chip and the multi-layer carrier. For example, a chip may have a CTE of 3 ppm/° C. while an organic chip carrier may have a CTE of 17-24 ppm/° C. Such a CTE mismatch can lead to bending of the carrier. If a heat spreader or lid is attached to the back surface of a chip with a thermal interface material, such as a thermally conductive grease, an uneven grease-filled gap can result between the chip and the heat spreader or lid. The thermal interface material can also be stretched as a result of the bending of the carrier which can impact thermal performance adversely. In a severe situation, cracking or debonding of the thermal interface material can occur.